Telephone system



April 7, 1942. B. KUDRNA ETAL 2,273,548

TELEPHONEv SYSTEM y Filed March so, 1959 'r shetssheet 1 Nr N N April 7,1942.

B. KUDRNA E-ru.r I

TELEPHONE SYSTEM Filed March 30, 1939 7 sheexs-snet 2 N w mw" SE H En:

INVENTORS: BENEDIKT KUDRNA ROMAN SCHWARTZ April 7, 1942. B. KUDRNA ETALTELEPHONE SYSTEM Filed March 3o, v19:59

7 Sheets-Sheet 3 BENEDIK ROMAN Z April 7, 1942. B. KUDRNA ETAL TELEPHONESYSTEM 7 Sheets-Sheet 4v Filed March 30e 1939 RTZl April 7, 1942.

B. KUDRNA ET AL TELEPHONE SYSTEM Filedmarch so, 1939 7 sheets-sheet 5:AZ MNT v GWR E w G MUA m WKN. m WTC A KS MN EA NMZ Eo BR @SRS Q SSS n:/w QNGQNQQwmvmw`mvt w hm@ \s SBS Se. EN@ kn. Y@ k E@ j E Bmw EN xt? .N

April 7, 1942. B. `KUDRNA ETAL. 2,278,548

TELEPHONE SYSTEM Filed March 30, 1939 l 7 Sheets-Sheet 6 vim# April 7,1942. B. KUDRNA ETL TELEPHONE SYSTEM 7 sheets-sheet 'I Filed March 30,1959 Patented Apr. 7, 1942 TELEPHONE SYSTEM Benedikt Kudrna, Vienna, andRoman Schwartz,

Berlin-Wilmersdorf, Germany,

assignors to Fides Gesellschaft fr die Verwaltung und Verwertung vongewerblichen Schutzrechten mit beschrnkter Haftung, Berlin, Germany, acorporation of Germany Application March 30, 1939, Serial No. 264,902 InGermany Api-ii 1, 1938 Claims.

The present invention relates to party lines in remote signalling, inparticular telephone installations in which for the selecting of arequired branch set selecting impulses of different duration anddirection control condenser receiver arrangements at the branch set. Inknown arrangements a selection among six sets is possible, since thecondenser arrangement at the individual branch sets are controlled bypositive or negative impulses of short, medium and long duration duringthe selector operation.

The present -invention has as its object the increasing of the number ofbranch sets which can be connected to the party line .and selected byselecting impulses of various duration and direction and in order toobtain this result a selecting current of particular direction andduration marks a number of branch sets Whose connecting relays at theend of the selecting current are connected to the party line in a numberof different ways so that only the connecting relay at the selectedbranch set is maintained energized and the current source in theexchangey necessary for maintaining diierent energies is connected tothe party line in a manner peculiar to the selected branch set.

With the arrangement according to the invention the selection amongeight branch sets is possible by using only two selecting impulses i. e.positive and negative which are differentiated in their duration. Byfurther dividing up of the duration of the` selecting impulses thenumber of branch sets which can be selected is considerably increasedthus vfor example when the duration of the current is divided into threestages, namely, selecting `currents of short, medium or long durationeach of sixteen branch sets .connected to the party line can beindividually connected with complete certainty.

In the drawings two embodiments of the invention are shown. Figs. l-3show one embodiment and Figs. 4-6 the second embodiment.

In both embodiments party lines of the eight branch sets are considered.

Figs. 1 and 4 lshow the apparatus and circuits of the two branch sets.

Figs. 2A, 2B and 5A, 5B show the arrangements associated with the partyline in the exchange.

In Figs. 3 and 6 marking signals in the individual branch set of theparty linev are shown and the wiring of the arrangements providedequally at all the branch sets.

I. EMBopIMEN'r ACCORDING 'ro F1os. 13

(l.) The branch set ASt6 makes acall and is connected The subscriber of.the branch set `AStl takes upr his handset. The switch hook contactylihuI is closed and thereupon the switchhook huGII is Opened. Theringing circuit is completed: earth, contact Hb, winding I and II of therelay SpB, switchhook contacts huII, huSI, impulse Contact nsz',connection l', conductor la, contacts l2ba, S32/1|, idg, |511, Ic,winding I of the relay An, The relays S205 and An operate. The relayS116 short circuits the winding I at contact llsp and at Contact lsfplprepares a dialling circuit over its winding III.. y

The relay An connects this in a locking circuit: 4,-, contact ISICTZ,wiper 26 of the indication switch KWI, normal position of this, contactElan, winding Il of kthe relay An',-. At contact 22cm, the setting ofthe marking selector is prepared. The relay Ais connected over relay23am, to the conductor la. At contact Man the relay J is connected andopens Contact 257' and closes contact 257'. The negative `pole of abattery of I20V is applied to the conductor Ib over the resistance 2l.The lamps in the branch sets of the conductor lb light up. The B-relayis connected in series with the lamps operated. i

In the exchange the lamp Gla is not lit up, accordingly the relay Bacannot operate since earth is disconnected by means of contact 28u11.The energized circuit for the relays B6 and Bl at the branch sets AStand 'l extends as follows: HDV, resistance 2l, Acontact 26j, conductorlb, branch set ASti, connection 8, lamp GIE, winding II and I of therelay B5, earth and branch set ASH, connection 8, lamp GII, winding II'and I of the relay B1, earth. The contacts Ilb (AStland 29121 (ASH) areopened and the contacts .39126 (ASt) and 3|??? (ASH) are closed. The Brelays guard lall the branch sets not in the calling condition sincecontact 29171 and `the corresponding contacts, in the branch sets Asti,5 and are opened.

At the calling branch set ASt the relay Sp remains energized: earth,contact 3065, winding III of the relay S116, contacts l8sp6, 3256, huBI,nez', connection l, vconductor la, contact IZba, relay A, contact 33ul,resistance 34; The relay operates over the contacts: 35111` or H512, 36arelay VI, resistance 3l, At contact 330| a circuit is prepared for onlyV2, but this cannot yet operate due to the short circuit ex-` tendingover: Tt, contacts 3510 or I'l, 36a, windingsII and I of relay V2,contact 3812i and At contact 3912i a circuit is prepared over the rotarymagnet Dkwl of the indicating selector KWI.

The calling subscriberselects his characterizing digit 6, by operating aspecial finger hole in his dial switch for transmittingpre-.settingimpulse trains. All subscribers in making a call operate their dialAswitches in the same manner.

However only the impulses corresponding to their own characterizingdigit are sent out. After the transmission of these impulses therefollows the short-circuiting of contact ns1' on the closing of contactnsa. rThe transmission of the pre-setting impulse train can also takeplace in a different manner, e. g. automatically on the taking up of theinstrument or by operating the finger plate corresponding to thesubscribers own number.

In the exchange the impulse trains are transmitted by the relay A to therotary magnet Dlcwl of the marking switch over: contacts 22am, 4Iab,42h, 43a, 39vI, 44pl, 45p, rotary magnet Dlcwll During this impulsetrain the relay V2 is also energized since by the opening of contact 36athe short circuit for winding I and II is removed. At contact 461:2 itshort circuits its winding II and holds its armature attracted duringthe impulse train. After the wiper 20 of the marking switch KWI and theback contact has connected over contact ZBan to the relay Ba. L-

This relay is energized by the battery from I 20V connected over thecontact 267' and operates its contacts. The relay P is energized:contacts 491JI, 50an, relay P, Parallel to the contact 490| is contact5Iba, so that the relay P remains energized after the release of relayVI. Over the series of contacts I9'Ic, 52g; and 53p the relay J ismaintained energized after the opening of contact 24an.

The relay A is disconnected at contact 23cm. The contact 36a is openedand contact 48a is closed. The relay VI restores and among other thingscloses contact 59vI. Since now the contact I 2ba is open and contactElba closed, the connecting signal associated with branch set ASt isapplied to the party line.

In Fig. 3 the connecting signals associated with the individual branchsets in the party line are arranged in the form of a table. From this itis clear for the connection of each branch set a selecting impulse ofparticular polarity (negative or positive) and particular duration(short or long) is necessary and that further the holding windings ofthe connected relays are either connected to the conductor la or toconductor Ib.

In order to connect the calling branch set AStG a long negative impulseis necessary by which however branch set AStI is also marked. Theholding of the connecting relay R6 takes place over conductor Ib and theholding of relay R1 over the conductor Ia.

The selection of the connecting signal is performed by means of theindicating selector KWI operated by the presetting impulse tra-in thewipers of which are raised on to contact E. The long negative impulsemarking of the two branch sets ASt6 and ASt'I controls the condenserresistance arrangements at the branch sets of the following circuit:contact B, wiper 54 of the connected switches KWI, contacts 58k13,5512!, 68j, Elba,

62, 63, junctions 3, I, contact 64191, condenser Kol. earth. Also at thebranch sets 5 and 8 the conclensers are connected with two seriesresistances corresponding to the resistances 65, 66 (Asti). At thebranch sets I-4 the junctions I and 2 are connected. The condensers areconnected over the resistance 65, corresponding to the resistance at thejunction l and thence to the conductor Ia.

On the release of relay VI the relay Y is connected: -I. contacts 68pand BSDI, relay Y, winding I, This holds over winding II and the contactTuy. The relay J is disconnected at conftact 521/. Since a long impulseis necessary for selecting the branch set AStS the relay J must not yetrestore and open the contact 607' in the charging circuit for thecondensers at the branch sets. In order to slow up its release the relayJ connects the slow relay E: contact |9kr2. wiper 20, contacts 5, 577',relay E, The relay E switches over the condenser I3 from chargingcircuit extending over the normal contact 12e to discharge circuitextending over relay J. After the opening of the contacts 52g therefollows the discharging of the condensers I3 over Contact 14e and relayJ, during which the relay J holds its armature attracted.

After the release of relay J the first discharging circuit for thecondensers at the branch sets is closed over conductor la of the partyline s0 that the condensers discharge` The condensers at the branch sets5 to 8 are also discharged. Since the discharging circuit at thesebranch sets also extends as does the charging circuit over tworesistances in series at the branch sets AStS and AStl, e. g. over theresistances 65, B6 and 62, 63, those condensers after the interruptionof their first discharging circuit will have a charg ing which issuillcient to operate the start relays (e. g. relay R6 at AStE and relayR1. at AStI) when the local discharging circuits are closed.

The relay J restoring after the discharge o! the condenser 'I3 in theexchange among other things closes its contacts 259, 157' and opens thecontacts 26j, 601', 51j. The relay Ba in the ex- 1 change and also the Brelays at the branch sets remain energized since over the contact 16ethe current source I 20V is still connected to the conductor I b. Duringthe release period of the relay E earth is applied over the contacts11e, 15g', Elba to the conductor Ia and thus the first dischargingcircuit for all the condensers is set up at the branch sets.

The relay E restores and at contact 'Ile disconnects the current source-IZIJV maintaining the B relay energized from the conductor Ib. Thelatter is switched through at Contact 18e. The relay Ba in the exchangeand the B relays at all branch sets restore. At contact I2ba theconductor I a is switched through. The condensers of the branch sets aredisconnected from the conductor Ia and connected in local dischargecircuits over the normal contacts of the B relays. At the calling branchset AStB the local discharging circuit of the condenser KOB extends overthe Contact 80176 `and the winding I of the relay R6 and at the branchset AStI marked by the same selecting current (long negative impulse),over the contact 'IBb'I and the winding I of the relay Rl. The relays R6and R1 operate and among other things connect their holding winding byclosing contacts BITS and 82H. The same procedure results at the branchsets AStS and AStIl. At the branch set ASH. and also at the branch setASt5 the holding winding II of the connecting relay is connected overthe junction 1 kwith the .conductor la while at lthe branch sets AStBand AStB the holding winding II of the R relay is connected over thejunction 8 to the conductor lb.

The connecting relays of the group marked by the same selecting current(long negative impulse) are connected in various manners to the partyline and actually in the branch set (AStB and AStI) to the conductor Iband in the branch set AStl is to the conductor la,

Since the branch set AStG is to be connected at this branch set thewinding II of the relay R is connected with the conductor lb and theunearthed pole (-l of the central battery is connected to this conductorin the exchange fat the conductor Ib over resistance 34, contact 33m;relay A, contacts 833/, Ellw. Holding current can accordingly not flowover the Winding II oi the relay R1 connected to the conductor la and tothe branch set ASH marked by the same selecting current as the branchset AStE. The connected relays R at the branch sets AStS and AStS arealso energized in the discharging circuits of the condensers. Theholding winding of the relay branch set ASr is connected to theconductor la according to Fig. 3. This relay cannot hold and thereforerestores. The holding winding of the start relay of the branch set AStSas well as those of the calling branch set ASt are connected to theconductor lb. However, this relay also restores since the holdingwinding is connected in similar manner to that at the branch set AStl i.e. in the opposite d`irection to that of the branch set AStG. Thejunctions 4, 5 and 5, 8 are connected together. The holding circuit overthe winding II of the start relay at the branch set ASM thereforeeffects a reversal of the polarization so that 4this startrelayrestores. Therefore only the connecting relay R5 at the branch set AStremains energized.

In the holding circuit of the Winding II of the relay R6, the relay A inthe exchange operates and at ttc connects'the relay Vl. Since the relayY is also energized the conductors '106 and 101 extending to thepreselector VW are switched through Aat the contacts lzia and Iy. Thecalling .relay of the preselector, not shown, closes the circuit overthe choke DTZ. The preselector is set on a free outgoing junction line.

On the energization of the start relay R6 there follows the connectionof the talking apparatus, which is indicated by the -microphone Mi, tothe party line. In addition to the circuit of the winding II of therelay R6 the following circuit is 1' completed: contact 8Std. choke Drl,contact |0011, llw, iZba, conductor la, contacts nsi. huI, lflr, windingI of the relay S6 operators equipment, contacts ltb, HG1-6, connection8, conductor lb, contacts 25j, 18e, Mw, 83g, relay A, contact 33m,resistance 36, The relay S6 operates. It closes the contacts Ilr and|08r6 parallel to the contacts Ills and H456 and disconnects earth fromthe winding II of the connected relay R5 at contact H235 this relayrestoring. At the same time the dissymmetry in the talking conductorsbrought about after the selection of the branch set ASt by theconnection of the winding II of the relay R6, is

removed. At contact ||3s6 the winding I of the relay B6 is.short-circuited. The contact 3285 is also opened.

The connection of the branch set AStB to the party line is completed.

After the opening oi the contact 69o! the relay til) Y in fthe exchangeremains energized over its winding II and the contacts 1011, 68p.Further the relay Vl undertakes the necessary switching operations forsetting up the connection to be extended from the calling subscriber.

The transmission of the presetting impulse train not only results in theconnection of the marking signal associated with the calling set AStSbut also the preparatory connection of the associated meter Z6 in theexchange which is connected over the wiper |03 parallel to the blockingwinding of the cut-oil relay of the preselector VW. The connection ofthe branch set AStE by means of a long negative impulse operating on thecondenser resistance arrangements and also marking the branch set AStlhas been described and how by the various connections of start relays ofthose branch sets AStB and ASH to the'party line, in conjunction withthe connection of the unearthed pole of a battery determined by theselecting operation (to the conductor ib) only the connection of abranch set (AStS) is iinally brought about.

By every other selecting current whether it be different in direction or`duration or direction kand duration a number of other branch sets (inthe embodiment always a group Kof two branch sets) are marked. Thus thelong positive im-- pulse marks the branch sets AStS and Ast-8 the shortnegative impulse marks the branch sets ASH! and ASt3 and a shortpositive impulse marks the branch sets AStI and ASt. vThe "finalconnection of the particular branch set always follows in such a mannertha-t the :start relay the previously vmarked branch sets are connectedin diirerent manner to the party line and only the start relay of thebranch set to be connected romains energized since for this relay asuitable holding circuit is set up in the exchange.

(2) Connection of the branch ser ASt with the branch set ASW 'lilacsubscriber of the branch set AStB wishes to speak with the subscriber ofthe branch set ASH.. He first selec-ts the marking digit for his ownline. The corresponding dial impulses voperate on the group and finalselectors and also on the indicating selector KW 2 on the party line.After this has been set corresponding 'to the subscribers digit `of thesame line the operating group and nal selector release. The completionand maintenance of the connection are performed 'by the apparatusassociated with the party line.

'.he relay P energized after the release of the relay An hasdisconnected the rotary magnet Diswi of the indicating .selector KW! atcontact 15p and. therefore over the contact M3@ the rotary magnet DkwZis brough under the control of the in ulse contact 43a. The circuit inthe rotary agnet Dkw is prepared at Contact Il9o by i s of the relay G.This relay is energized after the energizing of the relay Y: --lcontacts l'ip. Ii-ol, Hy, Hlh, relay 1G, It holds over its own contact498g during the time in which the .relay is restored.

By means `of the impulses sen-t out from the calling set the groupselector and the inal selec- .tor .in the exchange are set by means yofcontact wie also by means of the contact 43a of the marking selectorwhich acts as a discriminator. The characterizing digit of the partyline on which ythe branch sets ASt and AStl :are connected is 2422. Thediscriminator must accordingly be set by four impulse trains havingrespectively 2, 4, 2 and 2 impulses. If any of these 4 impulse trainsconsists of a different number of impulses there follows a disconnectionof the marking selector KW2 since then the condition is satisfied thatthese impulse trains have not suitable values ior setting up aconnection at the branch set on the calling party line and that aconnection with a remote junction line is to be seized. By means of eachimpulse train which operates on the marking selector its Wipers |20,|2|, and |22 are stepped on. All the contacts l8 are only shown aspassed over by the Wiper while of the contacts over which the wipers |2|and |22 are moved only contacts |||8 are shown since over the contacts|-|0 switching operations are performed which are oi no concern .for theconnection to be described.

By means of the rst impulse train the Wipers are seton the selectorcontact 2. After the release of the relay V2 energized during eachimpulse the marking relay Krl is energized: contacts |23ab, |24c2, wiper|20, switch contact 2, winding I of the relay KH, The relay Kr! locksup: contacts |25ab, |26lc1|, winding II of the relay Krl, resistance|21, At contact |281cr| it opens the connection between the contacts 5and 6 and connects the Winding I of the marking selector to the latterover its contact I29krl. Further the contact |30k1| in series with thewinding I of the marking selector Kr3 is opened.

By means of the second impulse train which has four impulses, theselector is set on the marking contact 6. |24o2 the marking relay Kr2operates and locks up over contact |30kr2 and its winding II. At contact|3|kr2 it opens the connection of the selector contacts 1 and 8 and atthe latter connects the holding winding II of the marking relay Krl overthe contact |32kr2.

The third impulse train brings the selector on to the marking contact 8.On the closing of contact |2402 the marking relay Krl is restored sinceits holding winding II is short circuited.

Positive is connected to the lower end of the winding over contacts|25ab and |28krl. After the closing of contact |24v2 positive isconnected also to the upper end of the Winding over contacts |23ab,I24v2, |20, 8, |32kr2.

|26kr| closed.

The last impulse train for marking the same line sets the markingselector on contact |0. Since the marking relay Kr3 is connected to thisselector contact with its Winding I over the series contact |30kr| and|34Icr2, it operates after the release of the control relay V2. Thus themarking signal which indicates that the connection with the branch setof the calling party line has been set up is sent out.

The relay Kr3 therefore locks up over its winding II and the contact|35kr3 by opening the contacts |36kr3 and |31kr3 and disconnects itsselector contacts 9 and and I4 and I5. At Contact |38kr3 an energizingcircuit for the relay HI is prepared and contact |39kr3 the conductor|01 is disconnected. In this Way the release of the set selector isinitiated at the exchange since the loop maintaining the bridge relay ata subsequent point in the connecting path is opened over the choke Dr2.

If any of the impulse trains do not have the value for marking its ownline the setting of the wipers of the indicating selector one after isopened and the contact |30kr| is After the closing of the contact o Thecontact Lil) another on the marking contacts 2, 6, 8 and I0, does nottake place. If, for example, the second train consists of 2 impulses andnot 4, then at the end of these impulses the Wipers |20 rest on theselector 4. The relay Ab operates and over its contact |40ab the windingII locks up in dependence on |4|v| of the slow-to-release relay VI.

The contact 4| ab in the circuit of the rotary magnet DkwZ is opened andhence this rotary magnet is removed beyond control by further impulses.These act exclusively on the numerical impulse acceptor of the exchange.

After selecting of the required branch set ASH the calling branch settransmits a final impulse train consisting of seven impulses by whichthe wipers of the indicating selector are set on the contact Il. In thisWay the connecting signal for the required branch set AStI is determinedwhich as is clear from Fig. 3 consists of a long negative impulse. Therequired branch set accordingly has the same connecting signal as thecalling branch set AStS.

The relay Kr3 on its operation has disconnected, the indicating selectorKWI, operating on the connection of the calling branch set AStB, byopening the contact |421cr3 and over the contact 581cr3 has connectedthe wiper |22 of the marking selector KW2, in preparation. The relay Hoperates: relay H, contacts |381cr3, |43v2, Wiper |2|, selector contact|'|,v contact |44ba, and at contact 202k locks up in dependence oncontact I'llm. The relay G is disconnected. The relay J is energized:contacts |45w, |4671, relay J, resistance |98, and over the contact 267'connects |20V to the conductor Ib. At all branch sets the B relaysoperate and connect the condenser resistance arrangements to theconductor la. Thus the relays BS and B1 are connected at the branch setsAS'LG and ASH. Further the relay BA in the exchange is energized and byopening the contacts |44ba removes the short circuit for Winding II ofrelay U| which relay operates. The opening of contact 251' results inthe release of the relay A. The relay VI restores and at contact 59mconnects the wiper 22 of the marking selector KW2 which rests onselector Contact and is thus connected with potential on the conductorlo.. At ali branch sets the condensers which are connected over one ortwo series resistances with the junctions 1 and hence with the conductorla, are charged. At the required branch set ASH this charging circuitextends over the resistances E2, 63, the junctions 3, the contact G4117and the condenser Kol to earth.

In the calling branch set A855 the energizing of the relay B6 alsoresults in the opening oi the speech circuit since the contact Hight isopened. The relay S6 holds over its winding II which is connected to theconductor |b over the contact l4lb.

At the same time as the relay J, relay W in the exchange is alsoenergized: contacts 63p, 6911!, |487L, relay W, At contact |4511; therelay J is disconnected. Since a long-impulse is necessary forconnecting the branch set ASH the relay J must not release after theopening of Contact |4511). Its release is delayed by the discharge ofthe condenser i3 over its winding. The relay E controlling the chargingand discharging of the condenser 13 is connected over its winding II:contacts |23ab, 124712, Wiper |20 and selector Contact Il of the markingselector KW2, Contact |499, Winding II of relay E, At contact 12e itopens the discharging circuit `of the condenser 13 and connects thisparallel "to relay J at contact 14e. After the `discharge of thecondenser 14e the relay J restores and among other things opens itscontacts 695i and I49j and closes its contact 157'. The charging circuitover the conductor la is interrupted. 'Ihe relay E is disconnected.Since it has a slow armature release the contact 11e is closed for ashort period. A pre-discharging circuit is again set up for thecondensers at the branch sets. The potential |V maintaining the relays Bat the branch set energized is connected after the closing of contact jover the contact 16e to the conductor Ib during the release period ofthe relay E. At the same time after the release of relay E there followsthe disconnection of the current source I20V from the conductor Ibatfcontact 18e and the interruption of the pre-discharging circuit overthe conductor la (at contact 11e).

When -l20V is disconnected from the conductor Ib the B-relays in thebranch sets yrestore. The release of relay B6 at the .calling branch setis delayed however since its winding I is short-circuited at-contactH336. The relay vBa. in the exchange restores. The conductors la and lbare switched through at the contacts 121m and 18e.

As already described. in the discharging circuits of the condensersclosed at the branch set after the release of the B-.relay only theconnecting relays at the branch sets ASt-S operate, since the condensersof the branch set Asti-4 are discharged and `connect their holdingwindings. At the calling branch yset AS'LB earth is disconnected fromthe winding II of relay R6 at contact H236. This relay cannot hold.

Of the connecting relays of the branch sets 5, 1 and 8 only theconnecting relay R1 of the required branch set can hold its armatureattracted. 'Ihe winding II of this connecting relay R1 isconnected'tofthe conductor la. When the bran-chset ASS which is alsomarked by la long negative impulse is not in its calling condition thewinding IIof its connecting relay R6 .is applied to the conductor lb. Inorder to maintain the relay R1 energized 4and hence to complete theconnection of the branch set 'ASt1 it is necessary in the exchange .toconnect the unearthed pole of an operating batteryzto the conductor laand earth to the conductor Ib. These operations are carried out asfollows: the wiper I 2| of the marking selector KW2 rests on contact I1.After the operationof relay Ba .and the removal of the short circuit .ofWinding II of relay Ul at contact l44ba this relay is energized. 'Illerelay U2 is connected at 89m and sets up a holding circuit over thewinding I of relay Ul at. contact 95u2. With attention to the callingbranch set ASt already connected to the party line a switching of thepole/from the conductor Ib to the ronductor mand of earth from theconductor Ia, to the conductor Ib cannot be carried out since theenergized relay S8 vat the branch set AStE has its polarizationreversed, which results in the restoration of its armature. The contactsIIIsB and IMSS are opened and the branch set AStB disconnected.Therefore` at the conductor la the unearthed pole of the battery isconnected and earth to the conductor Ib, A change in the currentdirection over the party line does not occur.

The switching over from 60V on the conductor lb to +60V-on `theconductor la takes place in two stages. First +60V is connected overhigh resistance 94 and the contact 9211.1 to the conductor la as well asearth over thehigh resistance 93 and the contact 9Iul. Thereupon therefollows a disconnection ofearth from'the conductor laat contact-89ul andof -BDV from the conductor Ib at contact 33ul. If the slow relay U2 hasalso attracted its armature -i-BUV is connected over the low resistance98 and the contact 99u2 to the conductor la and earth over the lowresistance 96 and the contact 9111.2 at the conductor Ib. vMicrophonefeeding current now flows over the party line at full strength.

The relay W completing the selecting impulse has by its energizationremoved the short circuit for windings I and II of the diierential relayX by opening the contacts Ilw and 8410. The winding II of relay R1 ofthe branch set ASt1 is therefore connected in the following holdingcircuit: -l-GtV, resistance 98, contact 99u2, choke Dri, contact g,Winding I of relay X, contact Mba, conductor la, branch set ASH,junctions 1, 5, winding II of relay R1, junctions 6, 4, contacts 8211,|02s1, earth. After the release of the relay B6 at the calling branchset thecalling circuit exists over the latter: from the conductor laover junction 1, contacts ns1', huI, H4s6, relay Sii, winding I,contacts l09b6, llls, junction 8, conductor lb, contacts 25j, 18e,winding 'II of relay X, contact 8'3'y, relay A, contact 91122,yresistancezSB, earth. The relay A operates. Further however, owing tothedissymmetry of 'theline in the exchange at the called branch set ASt1caused by the connection of the winding II of relay R1 to the conductorlla the difference vrelay X is energized since over its Winding Istronger current flows than over its Winding II. In this way theautomatic periodic callingioi the branch set ASH is possible.

The contact |151: in the circuit of the relay Vl is opened. Since alsothe contact 35u: is opened the closing of contact 36a cannot bringabout'an energization of the relay Vl by means ofthe correspondingbridge relay lA so that a premature disconnection of the ringingcurrentlby disconnection ofthe relay W is avoided.

At contact `|5Iw after the closingfof'contact |52ba a circuit iscompleted over the winding I of the relay Ab. The .relay Ab among otherthings disconnects at contact |25ab the holding circuit of the energizedmarking relays `Kr2 and Kr3. The relay Krl is alreadyrestored during theselecting operation.

Over the contact |5011 the relay W cornpleted a circuit for the callrelay Rr. The relay Rr operates e. g. every 5 seconds by connecting thepole over the time switch 'Ihe winding II of the connecting relay R1 'ofthe selected branch set ASH is applied tothe conductor la. The vbell ofthis branch set is connected .to the conductor lb. Ringing current issent out from the exchange over these conductors over which the holdingcircuit forthe previously energized connecting relay extends. Theconnection for ringing current to one or other conductor is determinedby the same relays Ul, U2, which effect the connection of the unearthedpole of acentral battery to the conductor la, or lb. The relays UI andU2 are energized when one of the branch sets ASH, 3, 5 or 1 is selected.When these are energized the contact |52u| is opened and thus a shortcircuit of the winding I of the relay X during the call is avoided bytheclosing of the contact 153W. The contact |54u2 is opened, -so thataccordingly over the contact I 55M the alternating current source cannotbe connected to the conductor I a. By the closing of the contact I56u2the short circuit of the winding II of relay X and by the closing of thecontact |51u2 the application of ringing current to the conductor Ib isprepared, When the relay Rr operates under the control of the secondsswitch at contact |5011 it completes the short circuit of the winding IIof relay X and at contact I591r connects the alternating current sourceto the conductor Ib. The bell of the branch set`ASt1 is operated on eachconnection of call current over the following circuit: call currentsource, contacts I59rr, |51u2, 18e, j, conductor Ib, junctions B, 9,contacts 2201-1, bell, earth.

The differential relay X energized owing to the dissymrnetry of theparty line which is brought about at the branch set ASH prevents apremature energizing of the call relay M by opening of contact |6012.

When the subscriber oi the called branch set ASH replies the winding Iof the relay S1 is connected between the conductors Ia and Ib: conductorIa, contacts usi, hu1I, I6Iru, winding I of relay S1, speakingapparatus, contacts |6251, I63r1, junction 8, conductor Ib. The relay S1operates and closes the contacts |6431 and |6551 parallel to thecontacts |6Ir1 and IHSTI. Further it opens the holding circuit over thewind ing II of relay R1 at Contact |02s1. 'Ihe dissymetry of the lineset up at this branch set after the selection is thus removed.

The result is that in the exchange the differential relay X restores andcloses contact |1533. The relay VI can now operate: contacts |1511, 36a,relay VI, resistance 31, Further the contact |60 is closed. The relay PIoperates after the energizing of relay Vl: contacts IIIIvI, |13w,winding II of relay Pi, Also the relay M is energized: contacts IIIIvI,|6610, |601', relay M,

By the opening of contact |61m and closing of contact I68m -I- isconnected. over the contact I60c at the wiper |03 and thus to the meterZ5 of the calling branch set AStE. The meter ZG operates and registersthe connection set up with the subscriber of the calling party line.

At contact |1|m the holding circuit of the relay H is opened, this relayrestores and at contact I|1h closes the circuit for relay G whichoperates. By the opening of Contact 88g the relay U2 is disconnected,restores and at contact 95u2 disconnects the relay UI. The release ofthe relays UI and U2 results in the disconnec tion of the batterieswhose pole is unearthed and the connection of the normal operatingbatteries with unearthed pole. The switching over from +60V on to earthat the Contact Ia and from earth on to 60V at the conductor Ib takesplace in two stages. At first by the opening of the contacts 91u2 and99u2 the low resistances 96 and 98 are disconnected. There follows theclosing of contacts 33rd, 92m, whereby -BOV is applied. to the conductorIb and earth to the conductor Ia, and thereupon the opening of contactsSIuI and 92u| and thus the final disconnection of +60V from theconductor Id and earth from the conductor Ib.

Also in the switching operations there is no change in the currentdirection over the conductors Ia and Ib of the party line.

The release of the relay H also brings about the disconnection of therelay W by opening of the contact I 48h, At the contacts |0Iw and 8410the windings of the differential relay X are short circuited. Thecontact |1310 in the circuit of the Winding II of the relay PI isopened. The relay PI holds however over the parallel contact |14p| andthus prevents an operation ol' the,` preselector VW by keeping thecontact |15p| open. At contact I |171 the winding I of the relay G isconnected.

When at the termination of a connection the subscribers of both branchsets ASL'E and ASii hang up their telephone instruments then the feedingbridge relay A in the exchange restores. At contact 43a theslow-to-release relay VI short circuited and among' other thingsinterrupts the holding circuit of the relays Ab and PI by opening thecontact |4|v|. The relay PI restores quickly and at contact 44p| closesa circuit for the rotary magnet Dlcw2 of the marking selector' KWZ;rotary magnet 1316102, contacts ||3;n, MpI, 40m, winding III of relayAb, vertical oil' normal contact I11kkw2, interrupter RU, The relay ABis maintained energized by the current Ilowing over its winding III andprevents a release of the relay P during the release movement of themarking selector KWE since the contact I16ab remains closed. When themarking selector KWZ reaches its normal position the principal offnormal contact I1'lc7cw2 is opened, the relay Ab restores and at ContactI16ab interrupts the circuit oi relay P. Further at contact I18ab isprepared the release circuit for the marking selector KWI. This isclosed after the release of relay P and since the relay G still keepsits contact |19g open, extends as follows: rotary magnet Dkwl, contacts45p, 44pI, 400|, I18ab, relay G, winding II, rotary off-normal contactlllklcwl, interrupter RU, During the release movement the relay Gremains energized over its winding II. When the mark-- ing selector KWIreaches its normal position the principal off normal contact Ikkwl isopened and the relay G restores.

On the release of the relay P the relay Y is also disconnected atcontact 68p and sets back its contacts to normal. At contact ||4p thecircuit over the winding I of relay G is opened.

(3) Selection of the branch set AiSt6 over the final selector LW So longas the partly line is seized in the outgoing direction from a subscriberof a branch set the seizing over a iinal selector is prevented. At leastone of the contacts IBIg, IBZcm, |8311, |8411 is opened so that when thetest wiper |05 of the final selector sets on the required branch set e.g. AStI on its associated contact 6 the test relay Plw cannot operate.

Ii the partly line is free when the final selector sets on the junctionof the branch set AStIi the following test circuit is completed: -l-,test relay Plw, wiper |85, contact 6, resistance |81, contacts I8Ig,|82an, I83a, |84p, relay C, resistance |83, The test relay Plw carriesout the usual switching operations in the final selector. The seizingrelay C is connected over its contacts I89c in a holding circuitindependent of the contacts of the connection I8Ig to |849 and atcontact |90c the winding I of the relay PI to the wiper 56 of themarking selector KWL Further it connects the cut-off relay Tr: -l,contact 200e, rest contact 20| oi the preselector VW, wiper |10, cut-offrelay Tr, The relay Tr disconnects the calling bridge from theconductors |06 and |01 in known manner. At contact I69c the parallelpath of the winding of the cut-oi relay Tr which contains vthe meter Z6of 'the vrequired branch set is opened so vthat .on the energizing ofthe relay M occurring on the reply from the calling branch set andclosing of contact IGBm there is no energization ofthe meter Z6. Themarking selector `KWI which on the call from a branch set is set `by the.marking ypresetting impulse train and brings about the connection ofthe calling branchset by connecting the particular .connecting ysignalto the party line, serves also-on the seizing of the party line over anal selector to connect the connecting signal of the branch set selectedin the iinal selector. The contacts or the final selector are connectedwith the contacts of the contact bank passed over by the wipers v56 0fthe marking selector KWI.

The seizing relay C l:brings about the stepping on of the markingselector KWI by closing the circuit for the driving magnet Dkwl atcontact |920: rotary magnet Dkwl, contacts 45p, 4479!, 40m, I'I'Bab,|92c, vertical off-normal contact .19| lclcwll, interrupter RU, -l-. Themarking selector moves forward by one step. The principal contact|9|lcw| is opened and the principal contact Ikcwl is closed. The circuitfor the rotary magnet Dlcwl now extends over this contact and thecontact |'I9g. When the wiper 56 of the marking selector KWI rests oncontact 6 y and the relay PI is energized: Winding I of relay PI,contact |90c, wiper 56, contact 6' at the marking selector KWI and atthe iinal selector LW, wiper |85, test relay Plw, -I. The relay PIoperates and stops the marking selector KWI by opening the contact 44p|.

The relays H and A are connected: relay H, contacts ISSpI, |9417, -I-and resistance 31|, contact 33uI, relay A, contacts 2|2y, |95pI, IBiba,-i- (earth). Over the contacts 36a and 35u: or |151: the relay VI isconnected, which energizes the relay P over contact 49UI. The relay J isenergized: -I-, contacts |4510, |46h, relay J, resistance |98, In themanner already described -IZIBV -is connected over the contact 255i tothe conductor Ib. The B-relays at all the branch sets and the relay Bain the exchange operate. At contact |96ba the circuit over the relay Ais opened. The relay A and hence also the relay VI restore.

At the branch sets the B-relays have connected the condenser resistancearrangements to the conductor Ia. Thus e. g. at the branch set AStB thecondenser Ko6 is connected over the contact 61196, the junctions I, 3the resista-nce 66, 65 at .junction 1 and hence to the conductor Ia. Atthe branch set ASH the condenser is connected over the contact 64171,the junction I, 3, the resistances 63, 62 and the junction 'I at theconductor Ia. rIYhe condenserresistance arrangements at all branch setsare controlled by means of the selecting current associated with theselected branch set AStG by a long-impulse which also serves to selectthe branch set ASt'I.

Since the wiper 54 of the marking selector KWI rests on contact 6, islconnected to the conductor Ia after the closing of contact 590|. Thecondensers at all branch sets are charged in the manner described insection 1. Over the contact 69o! since the rcontact |48h is closed, therelay W is energized, and at Contact |45w opens the circuit of relay J.ySince for the selecting of the branch sets AStI (and also of the branchset ASt'I) a long impulse is necessary, the -release of the relay J isdelayed so that over the contact 517' and the wiper 2U fof themarkingselector KWI "the energized .relay E by opening .of contact `112eand lclosing Contact 14e connects the condenser '13 parallel to relay J.In kthe discharging circuit of condenser 13 the relay J yremainsenergized. After the discharge of the :condenser 11:3 .it lrestores,opens the contacts 665i, 267', 517' and closes the contacts 157, 2.57'.During the vrelease period of the relay E -I20V is still connected overthe contact 16e to the conductor Ib. During this period the pre-chargingcircuit -for the condensers at the branch sets is also closed again overcontacts 11e, 157', 6Iba. After the release .of the relay E therefollows the disconnection of -IZDV from the conductor Ib at contact 16h,the switching through of the conductor and at the same time theinterruption of the predischarging circuit at the contact 11e. After therelease of the relay Ba the conductor Ia is switched through at contactI2ba. By means of the pre-discharging circuit the condensers of thebranch sets AStI to 1| are discharged while the condensers of the branchsets AStB to 8 have still a sufficient charge to energize a relay in alocal discharging circuit. After the release of the B-relays at thebranch sets the R-relays operate at the branch sets ASt5 to 8 in thelocal discharging circuits of the condensers. Thus at the branch setsAStG and ASH the two relays R6 and R'I marked by means of thelong-impulse, are energized. Both relays connect their holding windingsII. Also at the branch sets AStS and 8 not shown the windings IIof theR-relays are connected.

The nal connection of one of the two by the branch sets AStB and ASHselected'by the same selecting current show connecting relays have theirwindings II differently connected to the party line one to the conductorIa, the other to the conductor Ib, is dependent therefore on which ofthe conductors Ia or Ib has the unearthed pole of the current sourceapplied to it. For the completion of `the connection of the branch setAStI the unearthed pole of the current source must be connected to theconductor Ib.

Over the contact of the marking selector KWI and the Wiper 55 the relayUI cannot be energized since its energizing circuit only-extends overthe contacts I, 3, 5 and 1. The contacts of the relay UI and hencealso-those `of the directly dependent relay U2 remain inthe normalposition shown, Since the relay W has been .energized as alreadydescribed 63V is connected over resistance 34, contact 33ul, krelay A,contact 837/, winding II of relay X, contacts 18e, 257', to theconductor Ib, so that the relay RS can hold its armature attracted. Therelay R'I of the branch set ASt'I restores since earth is connected tothe conductor Ia in the exchange. The R-relay of the branch set ASt5whose winding II is also connected to the conductor Ia restores for thesame reason as the relay R'I of the branch set ASt'l.

The winding II of the R-relay of the branch set AStB is also connectedto the conductor Ib as well as the winding 1I of the relay R6. `Howeverthis relay can also not hold since as was mentioned earlier the holdingWinding is connected in similar manner to the holding Winding II of therelay R1, i. e. the junctions 4 and 6 are connected with one another andthe junction 5 is connected to junction 8. The current flowing over theWinding II of the R-relay of the branch set AStB' therefore effects areversal of the polarization of this relay so that it restores.

From the above it `is'clear thatafterthe operation of the selectingdevices at the branch sets consisting of condenser resistancearrangements by means of a selecting current of particular direction andduration a group of two branch sets (e. g. the group consisting of thebranch sets ASt and 1) is selected. The start relay of each of thesebranch sets is connected to one conductor of the party line. Independence on the selecting operation the current source in the exchangefor maintaining energized the start relay of the required branch set isconnected to that conductor of the party line to which the holdingwinding of this start relay is connected.

If the branch set ASt1 was to be selected, then a long impulse wouldalso be sent out. It could however then only hold the relay R1 at thebranch set AStT since by the energizing of the relays UI and U2 in themanner already described the inner -I- pole of a battery is connected tothe conductor Ia and earth to the conductor Ib.

By the connection of the winding II of the relay R6 at the conductor Iba dissymmetry of the party line is brought about at the selected branchset so that over the holding circuit of the relay R6 not only th'e relayA but also the relay X opcrates. 'I'hus the automatic periodic callingof the branch set AStB is rendered possible. By the opening of thecontact |151: the energizing of relay VI is prevented. At contact |5Ilw`the call relay Rr is connected and under the control of the 5 timeswitch 5 is energized for example every 5 seconds and applies callcurrent to the conductor (la) which does not extend the holding currentto the connection relay. In the branch set AStI the bell rings.

When the called branch set AStG replies the relay S6 operates, closesthe contacts IIIsG, IIIIs and by disconnecting earth from the winding IIof the relay R6 at contact II2s6 removes the dissymmetry of the partyline. In the exchange therefore the relay X can no longer maintain itsarmature attracted but restores and closes the circuit for relay VI atcontact |1511: which relay operates. The relay M is energized: -I-,contacts I4IUI, |6610, |6032, relay M, The holding circuit of relay H isopened at I1 Im and by the release of this relay the relay W is alsorestored on the opening of contact |48h. The call relay Rr isdisconnected and the windings I and II of the y,

differential relay X are short-circuited at the contacts IIlIw and 84w.

The release of the relay H also results in the energizing of the relay Gover its winding I: -I, contacts II4D, I|5v|, IIBy, |I1h, winding I ofrelay G, The relay G closes the contact IIBg parallel to contact |I5vI,opens the contact |199/ and thus removes the short circuit over itswinding II. The contact I8|g in the seizing circuit is opened and atcontact 202g the short circuit of the seizing relay is prepared.

At the termination of the connection the subscriber of the branch setAStB hangs up his receiver and the relays VI and P restore. The circuitfor the rotary magnet Dkwl of the marking selector KWI is closed. Itextends as described earlier over the winding II of the relay G. Therelay G since its contacts |847), I83a, |82an and 202g are closed isshort circuited and restores. At the contacts |900 and |890 the circuitsfor the relays PI and C and the test relay Plw` of the final selectorare opened. The relay Plw restores and in the usual manner brings aboutthe release of the incoming connecting path not shown.

, branch set AS'LIE operate.

Il. EMBODIMENT ACCORDING To F1os. 4 'ro il `(l) The branch` set ASt15makes a call and 'is connected The subscriber at the branch set AStItakes up his telephone. 'Ihe switchhook contact hul 5I is closed, theswitchbook contact lLuISII is opened. The call key Ta|5 is pressed andthe following call circuit completed: key TaIS, contacts I5bI5, |6S27I5,relay T|5, switchhook contact huIEI, contact I1rI5, junction 8,conductor IaI, contacts I8wl, ISyI, ZIIabI, 2Ihl, winding I of relay P2,winding I of relay Anl,

The relay Anl in the exchange and T|5 in the The relay P2 in View of thehigh resistance of the relay T|5 cannot operate. The relay Anl connectsthe relay JI contacts 2276113, 23am, relay JI, resistance 24,-. Atcontact 257 I the relay J I disconnects the conductor IbI from therepeater and connects -I20V to it over the contact 2B7'I and theresistance 21. The lamps at all the branch sets and the lamp Gla in theexchange light up. All B-relays operate and among others, the relay BaIin the exchange, and at the branch set AStIE and AStIG shown, the relaysBI5 and BIG over the following path: -I20V, resistance 21, contact 267|,conductor IDI, branch set AStI5; junction 9, lamp GI I5, relay BI5,winding I, contact 3331MB, 34b|5 (40H5 is open), 35sI5, 36s|5; earth andat the branch set ASUS; junction 9, lamp GI IB, relay BIB, winding I,contacts 28spI6, 29bI6, or 30H6, 3|s|6, 32SIG, earth.

At all branch sets not calling the closing of a call circuit isprevented by an operating B-relay thus at a branch set AStIS by theopening of the contact 31bl6 in series with the key TaIS.

At the calling branch set AStIB earth is connected with relay T|5 overthe contacts 38H5 and 39b| 5, so that this relay also remains energizedafter the opening of contact I5bI5. After the opening of contact 34b|5since the contact 40H5 is opened, the relay Sp|5 operates in series withthe winding I of relay B|5. It opens the contact |6sp|5 and closes thecontact 4Ispl5.

The branch set AStIS belongs to group I as is clear from Fig. 6. At thisbranch set the junctions I3 and I4 are connected. There followsaccordingly during the release of the relay T|5 the momentary directconnection of earth over the contacts 39bI5, 38H5, 4Isp|5y junctions I4,I3, contacts huIEI, I1rI5, junction 8 at the conductor IaI and thus tothe call circuit. In the exchange the signal for the group I of thebranch stations in the form of an earthed con nection brings about theoperation of relay P2 which locks up at contact 42112 in a holdingcircuit overts winding II prepared at contact 43baI. By the opening ofthe contact Mp2 and closing of the contact 45212 there follows the rstpreparation of the circuit containing the meter ZI5 of the callingbranch stations AStI 5.

After the opening of the contact I6sp|5 in the bran-ch set the relay T|5restores and the contact 38H5 is opened in the exchange the relay Anlrestores. The relay WI is energized:-I, contacts 46lcr|3, 41anI, 48baI,relay WI,-. At contact I8w| it disconnects the windings I of relays Anland P2 from the conductor I al. The contacts 49ml and 50w| are opened.Over the contact 5Iw| the connection of the relay Ka. to the conductorIaI and over the contact 52w| the connection of the relay Kb at theconductor IbI are prepared. Further it connects the relay YI contacts57m-I3, 41am, 4baI, 53wl, 12ka, 13kb,

lh'IabI, relay YI,-. The relay YI locks up together with the relay WIover the contacts 15y| and 'I6abI. It closes a new holding circuit atcontact I3'IyI over the winding II of relay P2 and at the same timeprepares over this contact the holding circuit to be explained later forthe relays'Ka, Kb, N and Ha. At contacts 'I'lyl and 18g/I the closing ofthe feeding and impulse bridge for the calling subscriber of the branchset AStIS is prepared.

By the opening of the contact 23am the relay JI is disconnected. Itrestores and disconnects -I20V from the conductor Ibl. The relay Balrestores. The conductor Ial is switched through at `contact Ilbal andthe conductor IbI at the contacts 257'I, 58el. In the branch stationsthe B-relays are disconnected.

At the calling branch set the relay SM5 remains energized: earth,contacts 3Bsl5', 35sI5, relay Spl5, contact 54spl5, resistance 55,contacts 56h15, 51H5, junction 9, conductor IbI, conta-cts 257`I, 58eI,52wl, relay Kb,-. In this circuit the relay Kb cannot operate. Thewinding II of the relay RI5 of the branch set AStI5 is connected to theconductor IaI in series with the relay Ka in the following circuit:earth, contacts 59bI5, 608MB, junctions 4, 5, winding II of relay FIS,junctions 1, 6, 8, conductor IaI, contacts SIbaI, 5IwI, relay Ka,-. Bothrelays RI5 and Ka operate. In the exchange it is thus determined thatthe branch station belongs to group III.

The relay RIS opens at contact 5'Irl5 the circuit for the relay SPI 5,which restores and opens the contact BspIS. The relay SI5' is connectedover the contact 62H5 in series with the winding II of the relay RIS andoperates. It short circuits the relay RI5 at contact 63sI5. So long asthe relay RIS still holds its armature attracted earth is connected tothe conductor IbI and brings about an energizing of the relay Kbdetermining that the branch AStI5 belong to group VI, over the followingpath: earth, contact 68sI5, junctions I2, II, contact 69H5, junctionsI0, 9, conductor Ibl, contacts 257`I, 586|, 52wl, relay Kb,-.

The relay Ka is energized for the rst time and thereupon the relay Kb.As a result the relay Ha is energized:+, contacts 107m, I|kb, relayHa,-. It has connected itself in a holding circuit over its contact19ha. The connection of the meter associated with the calling branch setAStIS is further prepared at contact 82ha. The relays Ha, Ka, Kb, havefurther opened or closed the contacts ha, 8Iha, 83nd 84ka, 857m, Bcb.Iillb, which do not serve to connect the meter' Z Since both relays Kaand Kb are energized on the callof the branch set AStI5 both windings Iand II of the relays N are connected. Their circuit extends over thecontacts 887m and 891th and the holding windings II of the relays Ka andKb. The relay N is a differential relay. It cannot operate when thecurrent ows over both windings. In the meter connecting device the contacts Slm, Bln, accordingly remain closed and the contacts 9271 9311.remain open. The meter ZIE is connected over the contacts 82ha, BOn,45212.

By means of the control of the group determining devices in the exchangeconsisting of the relays P2, Ka, Kb., Ha and N by means of thecharacterizing signal for the group to which the calling branch setAStI5 belongs it is determined that this branch set is included in thegroups I, III and VI.

On the energizing of the relay Ka the holding circuit of the relay WIprovided with a slow armature release is opened at contact 127m. Therelay WI restores and since in the mainwhile in the branch set AStI5 therelay R|5 has also restored and closed its contact 51H5, the microphone`feeding circuit is closed. 'Ihe relay SI5' in view of its slow releaseholds its armature attracted for a certain period and thus the contact64sI5' and B5sl5 are still closed. The feeding circuit extends asfollows: (earth), choke, D13, contacts 94u3, 95w2, 11g, 49wl, GIba,conductor IaI, contacts I'Irl5, huI5I, 65sl5, speaking apparatus(indicated by the microphone M) impulse contact nsz`l5, relay SI5,contacts 64sI5', 56bl5, 51H5, junction 9, conductor IbI, contacts 257'I,58el, 50u21, |8yl, 96u22, 91u3, relay AI,

In the branch set AStIS the relay SI5 operates and closes its contacts66s|5 and 6'IsI5 in parallel to the contacts 64sI5', and 65sI5. Furtherat contact 35sI5 it opens the short circuit of winding II of relay SI5',which however does not operate for the time being since the contact54sp| 5 is opened and the lamp GI I5 has not lit up.

In the exchange the relay AI operates. It opens the contact 93aI andcloses the contact SSaI, so that the relay V3 operates: contacts SSIaI,IIl0w2 or 233ml, relay V3, resistance IUI, The relay V3 prepares thesetting up of a circuit in such a manner that by the opening of thecontact |0203 and closing of the contact I03v3 it brings the rotarymagnet Dkwl of the marking selector KW under the control of the impulsecontact IIlIIaI. Further from the contact operations carried out byrelay VI there follow the further operations described above.

At the contact I05al the choke Dr4 is connected in bridge to theconductors IIIB and IIJI which extend to the preselector VW. In knownmanner the call relay of the preselector VW not shown operates andbrings about the setting of the preselector on a free outgoing line.Parallel to the guarding and holding winding of the relay Trl shown isthe meter ZI5 of the calling branch set AStI5 connected over thecontacts I 08u22, I09cI, 82ha, BUn, 45122 in the same manner as a meterof an individual line subscriber.

(2) Connection of the branch AST15 and the branch set ASTI Thesubscriber of the branch set AStIS transmits an impulse traincorresponding to the junction line 24228 of the branch set AStIB. Thefirst four digits of this train serve to mark the fact that thisconnection is required with a subscriber of the same party line. Afterthis impulse train has had its eiect a switching operation is performedin the exchange resulting in the release of the impulse acceptor whichhas been set and the completion of the connection is performedexclusively by apparatus on the party line. For this purpose the impulsetrains operate on a discriminator on the party line namely on themarking selector KW.

The impulse trains sent out by the calling subscriber are transmittedfrom the relay AI by ymeans of contact IU5aI to the impulse acceptingapparatus of the group and final selectors in the exchange. At the sametime the setting of the marking selector KW, is performed so that oneach release of the relay Al the rotary mag net Dcw is connected:contacts IIDyI, IIIabI, IMaI, |0303, rotary magnet Dkw, On the cominginto effect of the rst impulse and closing of Contact 98aI the relay V4is energized since a short circuit of the windings I and II is removedat Contact 99aI: contact H2113, winding I and II of the relay V4,contacts IUDwZ, 236ml, Bilal, resistance IIJI, The relay V4 shortcircuits its winding II at contact H3114 and this remains energizedduring the impulse train. The release of the relay V3 does not takeplace owing to the momentary closing of contact 98a| occurring in eachimpulse to be transferred owing to the release period of this relay. Therelay V4 among other operations opens its contact |4114 and thus duringeach setting operation of the marking selector prevents the operation ofthe marking relay controlled over the wiper I i5.

At the end of the first impulse train consisting of two impulses themarking relay KrH is energized over its winding I: contacts HB1/I,Hlabl, H8aI, H4124, Wiper H5, contact 2, winding I of the characterizingrelay Krl The relay KrH locks up over its winding h: contact ||9y|,winding h, of the relay KTH, contacts |2Ukr|3, |2IkrH, At contact|22kr|| it opens the connection between the selector contacts 5 and 6over the contact |24kr|| connects the winding I of the marking relayKr|2 to the contact 6. The contact |23kr| I which is in series with thewinding I of the relay Krl 3 is opened.

By means of the second impulse train consisting of four impulses themarking selector KW is stepped on to the contact 6. At the closing ofthe contact H4114 the marking relay Kr|2 operates owing to the currentflowing over its winding I. At contact |25kr|2 it locks up over itswinding h. It disconnects the connection between the selector contactsl, 8 and 9, |0 at contacts I26kr|2 and I2Ikrl2, connects the reversewinding II of the marking relay Krl I over its contact |28lcr|2 to theselector contact 8 and by closing contact |29kr|2 prepares the operationot the marking relay Kr|3 over the selector contact I0.

By means of the third impulse train consisting of two impulses thewipers of the marking selector KW are stepped on to the 8th contact.After the closing of contact H4114 the circuit is completed over thereverse winding II of the relay KrH; contacts H6yI, H'Iabl, HBaI, H4114,wiper H5, contacts 8, |28kr|2,iwinding II of the relay KrH, contacts|20kr|3, |2IkrH, The marking relay KrII restores. At contact I2 krH itdisconnects its two windings II and 71, simultaneously and at contact|23lcr|| connects the winding of the marking relay Kr|3 to the selectorcontact I0.

When the 4th impulse train (2nd impulse) has stepped on the wipers ofthe selector, the relay Kr|3 operates. It closes its contact I 307cr|3and thus completes a holding circuit over its winding h. At Contact|3|kr|3 the connection of the selector contacts I4 and I5 is interruptedand at contact |32kr|3 the connection of the relays EI and the selectorcontacts I5 to I8 is prepared. The purpose of the relay El will beexplained later.

Since the 4 impulses mark the connection with I The lost marking relayKr|3 to come caracas When a connection is set up with a subscriberconnected to a distant line then on the first of the impulse trainswhich does not correspond to the calling number of the calling partyline, the marking selector KW is not set on the marking contact. Therefollows the immediate disconnection of the marking selector and itssetting by the further impulse is thus prevented.

If the first impulse train consists not of 2 but of 3 impulses thenafter the closing of contact HMM the wiper H5 rests on the contact 3.The disconnecting relay AbI operates and locks up in a circuit extendingover contacts |34y| and |35bI, At contact H'Iabl it disconnects thepositive pole on the wiper H5.

After the selection of the party line the calling subscriber transmits afurther impulse train corresponding to the junction number of therequired subscriber (AstIB) consisting of six lmpulses which set thewipers of the marking selector KW on to the contact I 6. After closingof contact I |4114 the relay El is energized. Thus the operation of thecondenser resistance arrangements at the branch set is insured by meansof the selecting current of definite polarity consisting of a longimpulse.

This last impulse train corresponding to the calling number of therequired branch set determines not only-the duration of the selectingcurrent operating the condenser resistance arrangement on the branchsets, but also its direction. As is clear from Fie. 3 the connection ofpositive is necessary for the selection of the branch set AStIG. Theconnection of or +'I2V to the conductor IaI is therefore dependent onwhether the relay AuI is energized or not in that '12Vis only connectedwhen the normal contact Ililmz'l is closed and I-`I2V only when theoperating contact; |38cm| is closed.

Since the relay Kr|3 is energized the relay Krl I operates and the relayAnI: -I, contact` HB1/I. relay KTH winding h, contacts l4lllcrl3, |4|v4,I42abl, wiper |43 contact I6, winding II of the relay Anl, The Contact|3IanI is opened and the contact I38an| is closed. A connection of plusfor operating the condenser resistance arrangement at the branch set isthus ensured.

The contact |4I114 in parallel to the contact |457cr|| is closed. Theclosing of the contact |467cr|| in series with the winding I of therelay Ahl is for the time being without importance. Over the contact|4IkrH since the contact |487c1-|3 is closed, the relay JI is energizedand opens the contact 25j| and closes the contact |20V is thus connectedto the conductor I bI. branch sets for example GZIS and GZIB in thebranch sets AStIS and ASUS shown are lit up. The relay Bal in theexchange operates and the B relays at all the branch sets. At thecalling branch set ASME since the Contact 35s|5 is opened the relay SI5'is also energized over its winding II and operates the contacts shown inthe drawings in their normal positions. Since the circuit over the relaySI5 and the talking apparatus is opened at the contact 56h15 the relaySI5 restores. At all branch sets the B relays have connected thecondenser resistance arrangements controlled by the selecting current.Thus at the branch set AStIS: earth, condenser KOIB, contacts |58b|6,|5'IsI6 connection 3, resistance 256, |56, connection 8, conductor |a|.At the calling branch set a similar branch of the 1 conductor |a| is notcompleted over the con- The lamp Gla in the exchange and at the denserresistance arrangement since the contact I62s|5' is opened.

In the exchange the` relay W2 is energized: contactv I49baI, Winding Iof the relay W2, wiper ISU, selector contact IE, resistance I5I, andlocks up over its Winding II: -I, contacts |83yl, I84w2, winding II,resistance |86, The short circuit for the Winding I and II of the relayXI is removed at contacts 95u22 and 96102. Fur.- ther the contact E IbaIis opened and the contact I52ba| is closed.

The relay AI restores by the opening of the contact 25M and opens theshort circuit for the relay V2 so that this operates momentarily. Therelay V3 restores. During the time in which the relay V4 holds itsarmature attracted the winding I of the relay Abl is energized: ContactI3dyI, I53v4, I45krII, Winding I of the relay AbI, The relay AbIconnects itself in a holding circuit independent of contact I53o4 byclosing the o contact I35abI. At contact IGZabI the previously describedcircuit extending over the winding h of relay KTH is interrupted. Therelay KTII restores and disconnects the relay J.

So long as the relay J I holds its armature attracted after theenergizing of the relay Bal, +l'f2V is connected over resistance |38,contacts ISSanI, I54lcrI3, |5571, IEZbaI, to the conductor Inl. With theexception of a calling branch station AStIE at which as alreadymentioned the 1 contact IBZSIE is opened, the condensers are charged atall branchv sets. For example at the branch set AStI shown, overjunction 8, resistances |56, 256, junction 3, I, contacts I5'Isl6,I58bI6, condenser KoIG, earth.

For the selection of the branch set AStI and also the branch set ASUS along positive impulse is necessary. Since the branch set AStI5 isalready in the calling condition there is at this branch set nooperation of the condenser resistance arrangement. If this branch set isalso in its normal position then as detailed in section 3 the condenserresistance arrangements at this branch set are operated so that theconnection of the branch set Asti 5 is prepared together with .l

theconnection of the branch set AStIS. The nal connection is thendependent on the conductor to which the necessary current source inexchange for maintaining the connecting relays energized is connected,i. e. Ia! or IbI, since the winding II of the relay R|5 is connected tothe conductor la! and the winding II of the relay RIG to the conductorIbI.

Since a long positive impuls@ is tobe sent out the relay J I must notrestore at the opening of l contact IdllcrII as a short positive impulseonly marking the branch set AStII or AStI2 would then be transmitted.The condensers of the branch set AStII or AStM are completely chargedand not the condensers of the branch set AStIS to ASME. At the branchset AStI5 the charging circuit is opened in known manner at contactI62sI5.

The delay in the release of the relay J! serves to bring about theenergization of relay EI after the last impulse train sent out from thecalling subscriber, which, relay opens the charging circuit of thecondenser 220 at contact 2I8eI and connects this over contact 2I9e|parallel to relay J I At the opening of the contact IrIIlcrII thecondenser 22e discharges over relay JI which holds its armatureattracted during the oW of discharge current. It only restores after thedischarge of the condenser 220. The prolonged connection of to theconductor I aI effects a comi ae.

pletion discharge of thecondensers at all branch sets atl which thecondenser resistance arrangements are connected.

After the release of the relay J I a predischarging impulse is completedover the conductor IaI, for the discharge of the condensers at thebranch sets selected by means 0f a selecting current of short duration.The contacts |551' I, 259' I, 2I1j I are opened and the contacts I 5971,257'I areclosed. During the release period of the relay El,disconneet-ed at contact 2 I'Iy I, -IZIIV is connected over the contacts22 IeI andv 25j I to the conductor IbI. The B relays all remainenergized. Over the contacts ISl-lei, |5971 and I52bo| earth isconnected to the conductor Ia'I.

After the release of the relay Ei the condensers of the branch sets AStII to AStI4 are completely discharged while the condensers on the branchsets AStIS to AStIS still retain a charge which is sufficient to`operate connecting relays in local discharge circuits e. g. the relayRIB of the branch set ASt I 6.

The disconnection of -IZDV from the conductor IbI by the opening of thecontact 22IeI results` in the release of the B relays in the branchVsets and of the relay BaI. At contact SIbaI the conductor IaI switchesthrough and the conductor Ibi at contacts 251' I, 58eI.

At the calling branch setAStIE the relay BI5 restores slowly since itswinding II is short circuited by the Contact ISIsIE'. The relay SI5however has a longer armature release than the relay BIS so that therelay SI5l after closing contact 56b|5 can operate over the contacts64sl5 and S5s|5 still closed in the feeding circuit again completed inthe exchange over the relay AI.

At the branch stations AStIB to I8 the condensers discharge over thewinding I and the R relays of this branch set e. g. at the branch AStIBand the condenser KOIS of contact I'I3bI6 and Winding I of the relayRIG. The holding Winding II of the R relays are connected to the partyline. At the branch set AStISwinding II of the relay RIG is connected tothe conductor IbI over the following path: earth, contacts huIGII,214MB, junction 4, 5, winding II of the relay RIS, junction 'I, 6,` 9,conductor IbI. At the branch set AStIB as is clear from Fig. 3 theholding winding II is also connected to the conductor Ibi, Whilev theholding winding of the relay at the branch set AStI'I is connected withconductor IaI.. At the last. mentioned branch set the R relays aredisconnected as after the switching through` of the party line earth isconnected over choke Dr3 to the conductor IaI and accordingly the relaycan no longer maintain its armature attracted. Also at the branch setAStI the R relay is disconnected although the holding winding isconnected with they conductor I l?! since the holding winding is in theopposite direction at this branch set to the holding Winding of branchset AStIG since the junction 6, 1, and 4, 5 are not connected with oneanother but as is shown in Fig. 3 the junction 4, 'I and 5, 6

The R relay of the branch set AStI8 has its polarization reversed andrestores.

Only at the branch set AStII does the relay Ri remain energized' sincethe holding current over the Winding II is the same as the current overthe Winding I. The reversal of the polarization does not take place.

By the connection of the holding Winding II oi the relay Rit) thediscriminator is set up in the party line. This has the result that inthe exchange after the switching through of the conductors for the partyline differential relay X in the feeding bridge of the subscribersoperates in the holding circuit of relay RIB. It opens the contacts H5xIand 236ml. A short circuiting of the winding II of the relay W2 isprevented during the energization of the calling relay RrI. Moreover therelay V3 cannot operate although contact 99a| is closed since thecontact IUOw2 is also opened. The contact H6113 in series with thecontacts H5zr| and I85rrI remains open. A short circuit of the windingII of the relay W2 is also prevented in this position by the closing ofcontact I85rrI.

There follows the callingr of the selected branch station AStIB. Therelay Rrl is energized at definite time intervals for example every 5seconds: relay RTI, contact I6'Iw2, call switch 5", and closes contactsI6811'I and HDrrI. Over the first mentioned contact ringing current isconnected to that conductor in the present case IaI, over which theholding current for the relay RIB of the selected branch set AStIB doesnot extend. rlhe contact HIlrrI is connected in series with contactI66u3 and short circuits the winding I of the relay XI. The ringingcurrent takes the following path: A. C. source, contact IGBTTI,condenser, contacts HIu3, I65w2, 'HyI, 49wl, 6Ibal, conductor IaI,branch set AStIS, junction 8, I0, contact H41-I6, bell, earth.

When the called subscriber at the branch set AStIE takes up his handinstrument the short circuit for the winding I of the relay SIG isremoved at contact HZhuISII .It operates and closes its contacts HIsIB,HIsI6, H8sI6'. At contact II'sIB the winding II of the relay RIS isshort circuited and at contacts HIsIB and H8sI6 the connection of thetalking apparatus in bridge across the conductors of the party line isprepared.

The relay RIG restores and closes the contact H9rI6. Over this contactand the contacts I`I`IsI6 and I'IBSIS the relay SIB holds its armatureattracted after the opening of the contact 2`I41I6 ln view of its slowto release properties, the talking apparatus is in series with the relaySIB in the following connection bridging the party line: conductor IaI,junction B, contacts I801'I6, huIBI, H8sl6, operators equipment impulsecontact 113116, relay SIS, contacts IHsI6,I8IbI5, H9116, junction 9,conductor IbI. The relay SIS operates and maintains the circuitdescribed above by closing contacts I82s|6 and I83sI6, parallel tocontacts Hsl' and HIsIB after the release of relay SIB'.

By the opening of contact 2141'I6 the discrimi nator in the party lineat the selected branch set is removed. Then as a result in the exchangedifferential relay XI restores. Over the contact 236ml the relay V3operates and closes contact H6113. On the next energization of the relayRTI the holding winding II of the relay W2 is short circuited over thecontacts H51vl, I85r1'I, H6113. The relay W2 restores and opens thecircuit of the relay RrI. At the same time at the contacts 95u12 and961112 there follows the short circuiting of the windings I and II ofthe dierential relay XI so that during the conversation over themicrophone feeding circuit only the relay AI and the choke Dr3 areconnected.

At contact 234113 the relay YI is further held after the opening ofcontact 2I3w2.

The release of the relay XI on the reply of the subscriber of the calledbranch set AStIB is the reply signal which results in the connection ofthe meter ZIE and the calling branch set in the following local circuit:contacts I8l113, I 88ml, ISSwl, IilcI, meter Zi, contacts 82ML, 9011,45112, On the release of the relay W2 the Contact IE5-i102 is opened andthus the circuit of the meter ZIE is interrupted again.

When at the end of the conversation the subscriber of the branch setsASUS and AStII hangs up his apparatus the relays AI and VI restore. Therelay VI is the reuease relay and sets back the apparatus in theexchange to normal and closes the circuit over the rotary magnet Diaw atcontact M2113 which is completed alter the release of relay YI: magnetDkw, contacts |3203, I38yl, 265m, winding II of the relay Abi, contact|397c7m11, interrupter Unt, In the rest position of the marking selectorthe Contact I3$7cicw is opened. The selector is stopped, The relay Ablmaintained energized during the release operation of the selector KWprevents the party line from being seized so long as all the apparatusis not in its normal condition. since the Contact ISIIabI in theincoming ceasing conductor is open.

In the branch sets AStIS and ASUS the relays 5.15 and Slt restore.

For the final connection of a branch set determined by the selectingcurrent of either direction or duration. in contrast to the embodiment I(Figs. 1 to 3) in the present embodiment II (Figs. 4 to 6) the unearthedpole of the normal operating battery with its positive pole earthed isconnected in dependence on the selecting operation in the exchangethrough t0 the concuctor lai or conductor IbI. The current direction ishereby also reversed.

When the subscriber ol the branch set AStIB has made a call and set upe, connection with the subscriber of branch set AStIS then in theexchange by means of the relay U3 the n pole oi the battery is switchedover from the conduc tor IbI to the conductor IaI so that the relay RISwhose winding II is connected to the conductor icl is maintainedenergised. This current reversal does not result in the disconnection ofthe calling branch set AStIG since at this branch set the relay7 Sitenergises for the initiating of the call and restores during theconversation. During the connection of the branch set AStIS its repeatedenergisation by the current of opposite direction fiowing over the lineis ensured by means of the auxiliary relay SIE' which closes theenergising circuit for relay SI5 at contacts Hlsl, Haalt. .A specialsource of opposite polarity to the normal earthed operating battery isnot necessary.

(3) The branch ser ASt15 is selected over the final selector LW Afterthe setting of the test Wiper ISD of the iinal selector LW on thecontact I5 of the branch set AStIE the following seizing circuit iscompleted: -l, test relay P3111 oi the final selector, wiper IBI),contact l5, resistance IBI, contacts I92a11l, I93wl, |94al1l, IS5yI,relay CI, resistance ISB, The test relay Plw carried out the knownswitching operations in the final selector. The seizing relay Cl locksup over its contact IB'IcI in a holding circuit independent of thecontacts I92rml to I951/I, connects at Contact IQSCI the winding III ofthe relay N serving as a test relay for incoming trafiic at the wiper|99 of the marking selector KW and over Contact 2ll8cl, the contact RUZand wiper 203 of the preselector VW energises the contact of relay Trlwhich operates. At Contact 2El6ol conductor |01 is opened and thus anoperation of the preselector VW on the closing of contact l05a|occurring later is prevented.

At contact 204c| the circuit is completed for the rotary magnet Dkw ofthe marking selector: rotary magnetJ Dkw, contacts l02v3, |36abl, 204cl,oir-normal contact |klcw, interrupter Unt, On the first rotary step nofthe selector the off-normal contact lllklcw is opened and the olf-normalcontact l39kkw is closed. The rotary magnet `Dkw is now energised in thefollowing circuit: rotary magnet Dkw, contacts |0203, |38yl, 205n,305ab'l, off-normal contact |39kkw', interrupter Unt, -l. The markingselector operates untilthe wiper |99 rests on contact I5 which isconnected with the contact l5 of the nal selector. The following testcircuit is then completed: winding III of the relay N, contact |98cl,Wiper |99, contact l5 on the marking selector KW and on the finalselector LW, wiper |90, test relay Plw, The relay N then operates andopens the circuit of the rotary magnet Dkw. Further the 4relay Al isenergised: earth, conta-ct 2011/1, 20811., relay Al, At contact 99a| therelay V3 is connected.

By the setting of the marking selector KW the polarity and the durationof the necessary selecting current for connecting lthe required branchstation is determined. hence for the connection of the branch station along positive impulse is necessary which requires the energising of therelays Anl, Krl3, J l and Bal. The relay N connects the relay Krl3,contact 209n, 2l07cb, 2llka, relay Krl3, winding h, It closes itscontacts |54cr|3 in the selecting circuit and |40r|3 in the circuit ofwinding h of relay Krl This operates vin series with the relay Anl(winding II) contacts 209n, 2 |07cb,

2| lka, l3llkrl3, winding h of the relay Kr! l, contacts |40kr|3, |4lu4,|42ab|,wiper |43, contact l5 of the marking selector KW, relay Anl,winding II, The relay Anl disconnects: -12V at contact |31anl: atcontact |39anl: +12V. Over the contacts |48kr|3 and |41lcr|| the relayJl ener- .f

gised and at contact 257 -l2V is connected to the conductor Ibl Asdescribed the relay Bal is operated over the B relaysat the branchstations. The condensers at all branch stations are connected forcharging to the conductor lal. The relay Bal opens the contact Elbal inthe conductor lal and connects +12V to the outgoing conductor. Thecondensers at the branch sets are charged.

In the exchange since the wiper |50 rests on i For the selection and 5,

relay U3: l, contact lllllbal, winding I of the I relay W2, wiper |50,contacts l5, 2|2u3, relay U3,

Over the winding II of the relay W2 the .holding circuit is completed:contacts |83yl, |84w2, winding II of the relay W2, resistance |86, Therelay W2 closes the holding circuit for the relay U3 at contact 2|5w2extending over contact 2 l6n3.

The relay W2 energises the relay Yl over contact 2|3w2 and this relayoperates. At contact 11y| and 18y| the feeding .bridge is prepared. Therelay El is energised: contacts flltyl, ll1abl, l|8a|, H4114, wiper ll5,contacts l5, l32krl3, 20171, relay El, At contact 201y| the relay 4Al isdisconnected and restoresand at contact 99a a circuit over the relay V3is opened. The relay V4 operates momentarily and brings about anenergisation `of the relay El: contacts |34y|`, |5304, lllkrl |,fwindingI of the relay Abl, The relay El opens contact 2l8e| and over "contact2l9el connects the charged condenser 22 parallel to the relay Jl.Further the contact 58e| is opened and over the contact 22 lel theconnection of -|20V to the conductor Ibl is prepared after the releaseof the relay J l.

The relay Ablv connects itself in the holding circuit over the contacts|35abl and l3llyl. At contact |42abl itopens the circuit over thewinding I of the relay Anl and h of the relay Krl l?. In the first placeonly the relay Krll is restored since the relay Anl is maintainedenergised over its winding I: -l-, contacts 222bal, 223102, 224anl,winding I of the relay Anl,

The release of the relay Krl l results in the disconnection of the relayJ The relay J is however only momentarily held by the discharge currentof the condenser 220. Thus a positive selecting current of long durationis transmitted over the conductor lal and results in the completecharging of the condensers at all branch sets. yAfter the discharging ofthe Condenser 220 the relay Jl restores, closes the contacts |59gil,25y'l and opens the contacts |5571, 267'l and 201jl. At the lastmentioned contact the relay El which has a slow armature release isdisconnected. After the closing of contact 257`| therefore -|20V remainsconnected over contact 22|e| during the release period-of relay El atthe conductor lbl. In the time between the release of relay J l andrelay El earth is connected over the contacts lBllel, |595| and |52bal.Thus the pre-discharging circuit for the condensers at allbranch staltions is completed.

The condensers of the branch sets AStll to I4 which are alreadycompletely charged by a shortcircuiting current are completelydischarged since at these branch sets the junctions and 2 are connectedwith one another. At branch sets ASt|5 to AStlll the junctions l and 3are connected with one another. In the charging and pre-dischargingcircuits two resistances e. g. 225 and 226 are connected to the branchset AStl5. These condensers are only completely charged by a longimpulse and only partially discharged in the predischarging circuit.

After the release of the relay El in the exchange and after theopening-of the predischarging circuit the condensers of the branch setsAStl5, AStl still have sufficient charge to be able to operate relays inlocal discharging circuits.

The release of the relay El in the exchange also results in thedisconnection of V from the conductor lbl. The relay Bal and the Brelays at all branch sets restore. At the branch sets AStl to ASt|4 thecondensers are already discharged and the R relays are not energised. Atthe branch sets AStl5 to AStlS the R relays operate in the dischargecircuit and connect their winding II to the party line. At the branchsets AStl 5 and AStl1 these windings are connected to the conductor laland at the branch set AStlS and AStlB to the conductor lbl.

Therefore only the relay R|5 at the branch set ASt 5 must remainenergised.

By means of a long positive impulse both branch sets ASt l 5 and AStl 6are selected. Which of these two branch sets is finally connecteddepends on the conductor at the exchange to which the unearthed, pole ofthe operating battery is connected.

The winding II of the relay Rl5 of the required

